关键词: 长白山天池火山, S波包络展宽, S波包络峰值延时

Abstract: High-frequency S-wave seismogram envelopes of microearthquakes are broadened with increasing travel distance,which is called S-wave envelope broadening.Multiple forward scattering and diffraction for the random inhomogeneities along seismic ray path are the main reasons to cause the S-wave envelope broadening,so the phenomenon of S-wave envelope broadening is used to study the inhomogeneity of medium.The peak delay time of S-wave,which is defined as the time lag from the direct S-wave onset to the maximum amplitude arrival of its envelope,is accepted to quantify the phenomenon of S-wave envelope broadening.The 204 small earthquake records in Changbaishan Tianchi volcano were analyzed by S-wave envelope broadening algorithm.The results show that the phenomenon of S-wave envelope broadening in Changbaishan Tianchi volcano is obvious,and the peak delay time of S-wave has a positive correlation with hypocenter distance and frequency of S-wave.The relationships between the peak delay time of S-wave and the hypocenter distance for different frequency bands were got by statistics method.The results are beneficial to the understanding of the S-wave envelope broadening phenomena and the quantitative research on the inhomogeneities of the crust medium in the Changbaishan Tianchi volcano region.

Key words: Changbaishan Tianchi volcano, S-wave envelope broadening, peak delay time of S-wave